This section provides background information related to the present disclosure which is not necessarily prior art.
HVAC systems utilize aluminum or copper tubes to carry heat exchange fluid. In an evaporator or condenser of the HVAC system, the tubes may be arranged to meander back and forth in a serpentine pattern. At the bends of the serpentine pattern, a hairpin portion of the tube is present that, in general, is manufactured separately and then brazed to shorter sections of the tubes. Hairpins are expanded for proper tube to fin contact. Also, to ensure that the hairpin portion can be coupled to shorter sections of the tubes, the ends of the hairpin portions are expanded using an expansion device.
During expansion of the hairpin, a lubricant is needed to assist in the expansion process. To provide this lubricant, it is common to lubricate a coil of tube from which the hairpin portions are formed. In this regard, it is common to fill the entire master coil of tube with lubricant and then purge a majority or excess of the lubricant from the coil with compressed gas. The hairpin portions would then be cut at the appropriate length from the lubricated master coil. Alternatively, it is conventional to introduce large amounts of lubricant into the hairpin portions and then purge the lubricant from the tube using compressed gas.
These conventional methods, however, are very messy and expensive. In this regard, using these conventional methods, more lubricant than is necessary for expansion is used. By using more lubricant than is necessary, the cost associated to produce the hairpin portions is unnecessarily increased. In addition, the extra lubricant might have to be removed in a degreasing process after expansion, which also raises production costs.
What's more, the process of entirely filling the coil with lubricant is time consuming. Because of the long fill and purge times, the production capacity for a lubricating station is quite low. Due to the low production capacity of such a method, multiple lubricating stations are needed, which additionally raises the costs associated with producing the hairpin portions.
Lastly, the fill and purge process is generally dedicated to a single lubricant. More particularly, different lubricants may not be compatible with one another, and the fill and purge process generally utilizes a reservoir filled with a large amount of lubricant that is pumped from the reservoir to the tube to be expanded. Because of the incompatibility of various lubricants, the reservoir and lubricating machine must be thoroughly cleaned if a different lubricant is to be used so that no cross-contamination will occur. This is very time consuming, and not desirable.